Plan and apply separation in pipelines in Terraform - Step-by-Step Execution

Process Flow - Plan and apply separation in pipelines

Start Pipeline

↓

Terraform Plan Stage

↓

Review Plan Output

↓

Approve

↓

Terraform Apply

↓

Deploy Infrastructure

↓

End Pipeline

The pipeline first runs a plan to show changes, waits for approval, then applies changes to deploy infrastructure.

Execution Sample

Terraform

terraform plan -out=tfplan
# Review plan output
terraform apply tfplan

This code runs a plan to preview changes and then applies them if approved.

Process Table

Step	Action	Input/Condition	Result	Next Step
1	Run terraform plan	No prior plan	Plan file 'tfplan' created showing changes	Review plan output
2	Review plan output	Plan file exists	Changes understood, decision needed	Approve or Reject
3	Decision: Approve?	User input	If yes, proceed; if no, stop	Apply or Stop
4	Run terraform apply	Approved plan file	Infrastructure updated as planned	Deploy infrastructure
5	Deploy infrastructure	Apply successful	Infrastructure live and configured	End pipeline
6	Stop pipeline	Rejected plan	No changes applied	End pipeline

💡 Pipeline ends after apply or stop based on approval decision

Status Tracker

Variable	Start	After Plan	After Approval	After Apply	Final
plan_file	none	tfplan created	tfplan approved or rejected	tfplan applied or discarded	none or applied state
pipeline_status	started	planning	waiting approval	applying or stopped	completed or stopped

Key Moments - 3 Insights

Why do we separate 'plan' and 'apply' stages in the pipeline?

Separating plan and apply lets us review changes before making them live, as shown in execution_table rows 2 and 3.

What happens if the plan is rejected during approval?

The pipeline stops without applying changes, as shown in execution_table row 6.

Why do we save the plan output to a file before applying?

Saving the plan ensures the exact reviewed changes are applied later, preventing unexpected updates (execution_table row 1 and 4).

Visual Quiz - 3 Questions

Look at the execution table, what is the result of step 1?

A Infrastructure updated as planned

B Plan file 'tfplan' created showing changes

C No changes applied

D User input required

💡 Hint

Check the 'Result' column for step 1 in the execution_table

At which step does the pipeline wait for user approval?

A Step 3

B Step 2

C Step 4

D Step 6

💡 Hint

Look at the 'Action' and 'Next Step' columns around step 3 in the execution_table

If the plan is rejected, what is the pipeline status after step 6?

A applying

B completed

C stopped

D planning

💡 Hint

Refer to 'pipeline_status' in variable_tracker after step 6

Concept Snapshot

Terraform pipelines separate 'plan' and 'apply' stages.
Plan stage previews changes and saves to a file.
Approval is required before applying.
Apply stage uses the saved plan to update infrastructure.
This prevents unexpected changes and improves safety.

Full Transcript

In Terraform pipelines, we first run 'terraform plan' to see what changes will happen. This plan is saved to a file. Then, the pipeline waits for approval to make sure the changes are correct. If approved, 'terraform apply' uses the saved plan to update the infrastructure exactly as planned. If rejected, the pipeline stops and no changes are made. This separation helps avoid mistakes and keeps infrastructure safe.